1. Field of the Invention
This invention relates in general to the use of light-sensitive polymeric compositions in the graphic arts to produce photomechanical images and in particular to improvements in the image-forming development of positive-working photoresist films and positive-working lithographic printing plates containing light-sensitive quinone diazides. More specifically, this invention relates to the use of certain developing compositions which provide improved results in the development of the aforesaid photoresist films and printing plates.
2. Description of the Prior Art
An important class of light-sensitive materials that is widely utilized in the graphic arts in the formation of photomechanical images is the class of quinone diazides. These materials enjoy extensive use in such important applications as positive-working photoresist films and positive-working lithographic printing plates. Exposure of the composition to actinic radiation results in a solubility differential between the exposed and unexposed areas such that treatment with an appropriate developer results in removal of the radiation struck areas and retention of the desired image areas on the support. It is believed that such exposure decomposes the diazo structure in the radiation struck areas to form the free carboxylic acid group, thereby rendering the exposed areas soluble in alkaline developer solutions. The developer solutions which are employed for this purpose can be aqueous solutions or organic solutions. Typical examples of alkaline developer solutions utilized heretofore in development of quinone diazide compositions include solutions of sodium hydroxide, ammonium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate or sodium phosphate. Developers containing lower alcohols, ketones, or amines such as the alkyl amines, cycloalkyl amines and alkanolamines, are also well known.
An important requirement in the commercial utilization of the aforesaid photomechenical imaging processes is the ability to form a fine, highly detailed image pattern. This is particularly critical in the utilization of photoresists in the semiconductor industry, for example, in the manufacture of integrated circuit devices. One of the problems restricting the capability of producing the desired fine image detail is contamination of the surface of the substrate by metal ions such as sodium or potassium ions, which are present in the developer solution. Contamination with such ions can deteriorate the substrate conductivity and adversely affect important properties of the integrated circuit device such as electrical resistivity. In an attempt to overcome this problem, efforts have been made heretofore toward providing a developer solution that is capable of providing the necessary high resolving power yet is free of metal ions. For example, Japanese Patent Publication No. 56226/1976 entitled "Developers For Positive-Type Photosensitive Resins," published May 17, 1976, points out the advantages of a developer which is free of metal ions. This publication proposes the use of tetraalkylammonium hydroxides, such as tetramethylammonium hydroxide or tetraethylammonium hydroxide, as developers. It points out that tetraalkanolammonium hydroxides, such as tetraethanolammonium hydroxide, can also be used as metal-ion-free developers but suffer from the disadvantages of strong odor and a high degree of toxicity. The use of tetramethylammonium hydroxide as a developer for positive-working photoresists is also disclosed in British Pat. No. 1,367,830.